reports from the vatican. >> reporter: hey, rob, hey, diana. it's the beginning of the most solemn season on the christian calendar and pope benedict's long-time assistant told him and the entire ash wednesday audience that there's a veil of sadness in our hearts. pope benedict opened a 40-day period of humility. having sent his own humble and revolutionary message. no one is irreplaceable, even a pope. as i prepare to conclude, he says, i ask for special remembrance in your prayer. the 85-year-old looked frail, leading his final major mass in st. peters basilica. some recorded the moment on ipads, and the massive audience gave him a rare standing ovation. the pontiff looking moved. outside, we found the audience had been moved, as well. do you get the sense that people inside felt like they were saying goodbye to the pope? >> yes, very much so. i felt like that. when he left the altar and he was blessing everybody, we knew that would really be for the last time. and that makes you very emotional. >> this is a once-in-a-lifetime opportunity. how often can you say you went to the vatican f
